1. Field of the Invention
The present invention relates to a resin composition containing a polyacetal resin, a thermoplastic polyurethane and a specific polymer having a hydroxyl group at the end; and a molded article comprising the resin composition. The resin composition of the present invention is excellent in terms of mechanical performance such as tensile strength and tensile elongation, and impact resistance at ambient temperature and lower temperatures; wear resistance; and moldability. Therefore, the resin composition is useful as a material of a variety of molded articles.
2. Related Art of the Invention
Polyacetal resins have been used in wider fields as an engineering resin with good tensile strength and elongation, electrical properties, chemical resistance and thermal resistance. However, polyacetal resins have poor impact resistance, and therefore, as a method for improving the impact resistance, a technique of blending a rubber component has been known. In order that the rubber component might be finely dispersed in the matrix of the polyacetal resins to make the impact resistance effectively exerted, thermoplastic polyurethanes with a higher polarity have been used because polyacetal resins are highly polar. However, even a resin composition comprising a thermoplastic polyurethane blended in a polyacetal resin still remains to be improved, regarding the impact resistance at lower temperatures and the like.
So as to improve the polyacetal resins from the respect of the impact resistance at lower temperatures, the weatherability and the like, attempts have been made to add a styrene block copolymer to the resins. However, generally, such styrene block copolymer may not be dispersed finely; and when the resulting resin composition is modified into molded articles, delamination occurs severely while the tensile elongation is decreased markedly.
It has been known that a molding composition of a mixture of a polyacetal resin, an elastomer with a softening point below the crystallite melting point of the polyacetal resin and with a second-order transition temperature of -120.degree. C. to +30.degree. C., and a thermoplastic polyurethane, has good impact resistance (U.S. Pat. No. 4,277,577). However, the polyacetal resin-derived performance such as tensile strength and tensile elongation is severely deteriorated in the molding composition; and furthermore, the impact resistance may sometimes be insufficient for some use.